Project Summary Hypertension is a major health problem in Western Societies and a risk factor for stroke, myocardial infarction, and heart failure and therapies specifically targeted at mitochondria represent promising strategies to reduce target- organ-damage. Mitochondrial permeability transition pore (mPTP) plays a key role in mitochondrial dysfunction and target-organ-damage in hypertension. We discovered that depletion or inhibition of Cyclophilin D (CypD), a regulatory subunit of mPTP opening, improves vascular function and attenuates hypertension. Meanwhile, the tissue specific role of CypD and molecular mechanisms of CypD activation are not known. In the proposed studies, we will take this work forward by defining the role of vascular CypD and therapeutic potential to target CypD in endothelial dysfunction and hypertension. Our studies in human subjects with essential hypertension showed CypD hyperacetylation and implicate CypD activation by K166 acetylation due to imbalance between GCN5L1 acetyltransfe- rase and reduced Sirt3 deacetylase activity. Sirt3 is inactivated by highly reactive mitochondrial lipid dicarbonyls, isolevuglandins (isoLG), while isoLG scavenging prevents CypD acetylation and reduces hypertension. We propose targeting mitochondrial CypD to inhibit oxidative stress, improve vascular functions and reduce hypertension. The overall objective of this proposal is to define specific mechanisms of CypD mediated vascular oxidative stress and test the therapeutic potential of targeting CypD in hypertension. We will pursue the following aims: AIM 1. To test the hypothesis that cell specific CypD depletion in endothelial and smooth muscle reduces vascular oxidative stress, protects vascular relaxation and attenuates hypertension. In this aim we will examine the protective role of CypD depletion in inducible endothelial specific CypD knockout (EcCypDKO) and smooth muscle specific CypD knockout (SmcCypDKO) mice using AngII and DOCA-salt models of hypertension. AIM 2. To test the hypothesis that CypD-K166 acetylation contributes to vascular dysfunction and hypertension. We will define the pathophysiological significance of CypD-K166 acetylation using new deacetylation mimic CypD-K166R mutant mice, new endothelial specific GCN5L1 knockout mice (EcGCN5L1KO), and endothelial specific Sirt3 knockout mice (EcSirt3KO). All mice are available in our lab. AIM 3. To test the hypothesis that CypD inhibition and blocking CypD hyperacetylation after onset hypertension improve vascular function. We will test if CypD blockers improve vascular function and reduce blood pressure in hypertensive mice. We will study CypD acetylation in resistance arteries isolated from human subjects with essential hypertension and test if CypD blockers improve human endothelial function. We are in an ideal position to perform these interdisciplinary studies. We developed new CypD transgenic mouse models and mitochondria-targeted treatments. We have access to human vascular tissue and unique expertise in oxidative stress, human vascular studies and hypertension. Our data strongly support this novel pathway in vascular dysfunction, and this work has the potential to make a major impact on the development of new treatments.